Fix token usage for private git repositories and retrieve source package from the build-source job instead of obs-capture
This MR fixes several issues:
- the LAVA job was unable to retrieve gitlab artifacts for private git repositories due to wrong usage of token.
- the source package was retrieved from the obs-capture job, but this will no longer be possible to avoid capturing duplicated files on gitlab side instead we should use build-source's artifacts.
- use the lava-runner templating to pass several variables instead of hardcoding them in the LAVA yaml file.